I lost my troop leader once. No one seemed too fussed about that. I left him on the end of a pressle handset and 200 metres of don 10. Apparently myself and the tank were supposed to be on the other end.

I knew a particularly unpopular NCO who put his sidearm down on the tailgate of a landrover after posing for pictures in the middle of a vast mountain range a few years back. His blokes saw what he'd done, but such was his unpopularity that they turned a blind eye, let it drop off the back of the vehicle, and p*ssed themselves laughing when the sadistic cnut went to unload. And was court martialled.

1- SLR breechblock. On a recruit course- where I was a DS- ordered some pizzas one night, put my breechblock in the hip pocket of my trousers, jumped into a mate's MG, 'urtled across camp, got pizzas, returned and assumed 'wolfing' mode.
End of feed, check pocket...NO BREECHBLOCK! Cue frantic search in pitch dark- no result. In desperation, check car. There it was, on the door ledge (exactly the width of a breechblock) as perfectly aligned as if I had placed it there. Half an inch one way...gone under the seat; half an inch the other...gone into the night.

2- Prismatic compass. On exercise (again as DS) bangety bang bang, run back to platoon harbour, trip flying over blackboy stump. 24 hrs later, go to use compass...NO COMPASS!
Slink up to the normally even-tempered Pl SGT. and confess. With a muted intensity that would have made Hannibal Lecter quail, he leaned towards me ever-so-slightly and intoned 'FINDIT'
About 30 terrified seconds later I found it- right where I tripped over.